Here’s an FAQ about the Lodsys Patent Suits brought against iOS devs.
What a mess. It’s a great summary of a situation that will affect more than
just apps implementing In-App purchasing.

If Lodsys succeeds then other patent holders will feel emboldened to go after
large swaths of small devs for infringement. And the devs would most likely
cave in because defending a patent suite is much more costly than licensing.
This isn’t just limited to Apple. Developers on platforms from Google,
Microsoft and even web apps could become targets.